Methoxybenzyl ethers

Catalytic hydrogenolysis or treatment with trifluoroacetic acid (TFA) in water and dichloromethane (DCM)13 will also remove a PMB group. This protecting group is, however, reasonably stable to cold aqueous acetic acid. 

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These reaction conditions do not affect most of the other common hydroxy-protecting groups and the methoxybenzyl group is therefore useful in synthetic sequences that require selective deprotection of different hydroxy groups. 4-Methoxybenzyl ethers can also be selectively cleaved by dimethylboron bromide.182... 

Ether cleavage. 4-Methoxybenzyl ethers are cleaved with clay-supported ammonium nitrate on microwave irradiation (13 examples, 70-88%). No solvent is used. 

BenzybUion. The reagent is much more stable than the corresponding trichloroacetimidate. It is obtained by reaction of trifluoroacetonitrile, which is the dehydration product of trifluoroacetamide under Swem oxidation conditions, with 4-methoxybenzyl alcohol. Even tertiary alcohols form 4-methoxybenzyl ethers with this reagent. 

The direct synthesis of a /j-(l->2)-mannooctaose was achieved by a two-step iterative protocol from the key sulfoxide donor 275. After an initial coupling to cyclohexanol to cap the reducing end of the chain, the 2-0-(4-methoxybenzyl) ether... 

O-Dechloroacetylation of IV.61 by treatment with thiomea gave IV.62, which was subsequently reprotected as the hydrogenolyzable 4-methoxybenzyl ether with 4-methoxybenzyl trichloroacetimidate and triflic acid under phase transfer catalysis conditions [104]. Saponification of the benzoate and methyl esters with lithium hydroperoxide followed by methanolic sodium hydroxide and acidification then gave the acid IV.63. O-Sulfonation of IV.63 was achieved with the sulfur trioxide-tri-methylamine complex to give the disulfate IV.64 as the sodium salt. Finally, hydro-genolysis of IV.64 with Pd/C in aqueous methanol afforded the target disaccharide IV.51. 

Methoxybenzyl) 5-(2-pyrk 4-Methoxybenzyl ethers. derivatized under neutral conditn dichloromethane. 

Methoxybenzyl ethers. Alcohols (primary, secondary, and tertiary) are derivatized under neutral conditions with the title reagent in the presence of AgOTf in dichloromethane. 

The 4-methoxybenzyl ether group in the compound shown was preferentially removed in dichloromethane solution containing anisole and stannous chloride upon treatment at ambient temperature with trimethylchlorosilane during 30 minutes to give the product in 87% yield (ref. 187). 

Reduction of 4,6-0-(4-methoxybenzylidene)hexopyrano8ldes to 4-methoxybenzyl ether groups is referred to in Chapter 4> and oxidation of benzylldene acetals to hydroxybenzoates in Chapter 5. 

Reductive cleavage (LiAlH -AlCl, NaCNBH -HCl, or AlCl -Me N) of 2-substituted l 6-anhydro-3 -0-endo-(M-methoxybenzylidene)-B-D-galactopyranose derivatives gave predominantly the axial 3-0 -(4-methoxybenzyl) ethers with a free -hydroxy group. -Methoxy... 

The 2,4-dimethylbenzyl group is a protecting group for phenols that is reported not to be removed by hydrogenolysis at 1 atmosphere within the reaction time that is needed to cleave benzyl ethers, but it is removed if the pressure is increased to 4 atmospheres. The specific cleavage of 4-methoxybenzyl ethers of alcohols... 

The 4-methoxybenzyl ether protecting group can be removed readily and efficiently with DDQ (2,3-dlchloro-5,6-dicyanobenzoquinone) in... 

The 2 -hydroxy group of adenosine can be selectively blocked as a 4-methoxybenzyl ether, a new protecting group, by treatment with 4-methoxybenzyl bromide and sodium hydride. A mixture of the 2 -and 3 -ethers results if p-methoxyphenyl diazomethane is used in presence of stannous chloride. The ether protecting group was rapidly cleaved with trityl tetraf luoroborate. ... 

The Novartis process starts with the protection of the Roche ester 304 as a 4-methoxybenzyl ether. Reduction and subsequent oxidation furnished aldehyde (S)-15 that is ready for the Evans et al. aldol reaction (Scheme 10.58). It is interesting to note that (2,2,6,6-tetramethylpiperidin-l-yl)oxyl (free radical) (TEMPO)/bleach oxidation in biphasic conditions (water/CH2Cl2) produced the unstable aldehyde in quantitative yield. The Evans group syn-aldol... 

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